Fluoroelastomer has been widely used in sealing materials, containers and hosepipes for its excellent heat resistance, oil resistance and chemical resistance. Common fluoroelastomer capable of being vulcanized by using peroxide mainly comprises two broad categories: vinylidene fluoride-based copolymerized elastomers and tetrafluoroethylene-based copolymerized elastomers, such as copolymerized elastomers of vinylidene fluoride (VDF), perfluoropropylene (HFP), tetrafluoroethylene (TFE) and bromine-containing alkenes. The polymerization mode of fluoroelastomers mainly comprises two categories: emulsion polymerization and suspension polymerization. For emulsion polymerization, the polymerization is initiated mainly using a water soluble initiator (persulfates), and after the polymerization, the ion terminal group may be easily produced. For suspension polymerization, the reaction is initiated using an oil soluble initiator, and the resulted elastomer neither has terminal ion nor has emulsifier residue, but the obtained polymer has relatively small molecular weight.
In order to obtain necessary physical performances widely required, the fluoroelastomer must be crosslinked before use. Its vulcanization system is a mixture of organic peroxides and multifunctional unsaturated active auxiliary, while its crosslinking site is “I” or “Br” atom of “C—I” or “C—Br” bond on the fluoroelastomer.
As reported in domestic and overseas patents and literatures, the vulcanization point monomers mainly used for peroxide vulcanized fluororubber mainly are bromine-containing alkenes, iodine-containing alkenes, non-conjugated dienes, cyano-containing alkenes, etc., and bromine atom, iodine atom, “C═C” double bond or —CN, which are introduced onto the molecular chain of fluoroelastomer during polymerization, act as a crosslinking point during peroxide vulcanization. Patent CN1665852A discloses a peroxide curable fluoroelastomer. The fluoroelastomer adopts CH2═CH—(CF2)nI (n=2-8), of which the representative substance is 4-iodo-3,3,4,4-tetrafluorobutene-1, as vulcanization point monomer, and uses RIx (R is perfluoroalkyl group having 3-10 carbon atoms, X=1-2) as chain transfer agent. “I” atom, which acts as a vulcanization point during vulcanization, is introduced into the middle and end of the molecular chain of the fluoroelastomer respectively. Thus, the existing preparation for fluoroelastomer capable of being vulcanized by using peroxide requires the use of bromine or iodine containing alkenes, and has complex preparation process and high raw material cost.